Undercarriages are generally hinge-mounted to the structure of an aircraft, e.g. via two ball joints in alignment mounted on the aircraft in order to receive pivots that are secured to the undercarriage. A stabilizer member referred to as a “side-brace” serves, when the undercarriage is deployed, to hold it in the deployed position. The side-brace is then locked in position and triangulates the undercarriage to prevent it from pivoting about the axis defined by the pivots.
An operating actuator, generally a telescopic actuator, is coupled between the structure of the aircraft and the undercarriage in order to operate it. In general, the operating actuator is used actively to cause the undercarriage to rise towards its stowage position, and it is used to slow the downward movement of the undercarriage towards its deployed position.
It is known that when the undercarriage is deployed, it is subjected to forces due either to the deformation of the structure of the aircraft in flight, or else to forces coming up from the ground as a result of the aircraft running on the ground at an airport.
In general, since the actuator is mounted in parallel with the side-brace, it is liable to transmit forces that it must withstand, and it is thus liable to stress its couplings. Nevertheless, if the actuator is not rigid during these stages, as applies for example with a hydraulic actuator having its chambers connected to discharge once the undercarriage has reached its deployed position and been locked therein, then there is no risk of the actuator transmitting forces and thus stressing its couplings to any great extent.
However, that does not apply to an irreversible electromechanical actuator, nor does it apply to a reversible electromechanical actuator as from a certain force and that also presents a high level of internal inertia. An actuator of such a type can present stiffness that is very high, at least on a transient basis, thus constituting a path for passing forces that run the risk of heavily stressing its couplings and its internal components.